June 29, 2012

Melting Permafrost Threatens Swiss Villages

Melting glaciers are the most visible effect of global warming in
the Swiss Alps. Meanwhile, permafrost is invisible and melting too,
often causing rockfall and massive debris flows, ultimately
threatening mountain villages.

Guttannen, home to 310
residents, is a tiny village in the Bernese Alps, the last one that
travellers drive through on the way up to Grimsel Pass. It’s spring
and the snow is retreating from the steep slopes of the valley. As
the pass is still closed, calm reigns in the picturesque village
centre. Only cowbells and the rushing of the nearby Aar river break
the silence.

For some residents
though, living in Guttannen has become rather uneasy and, on the long
term, even dangerous. The root cause of the peril lies further
uphill, in the northeastern flank of the 3,282 metres high
Ritzlihorn. In July 2009, a huge rockfall had occurred and since
then, massive debris flows have roared downhill each summer.

“These mudslides as
well as the volume of transported rubble have grown from year to
year,” says Nils Hählen, hydraulic engineer at the cantonal public
works service. “The debris partly ends up in the Aar, lifting and
widening its channel.” Within three years, 630,000 cubic metres
were transported into the river, increasingly endangering civil
infrastructure.

In summer, after heavy
rainfall, the only road leading through the narrow valley often has
to be temporarily closed. A house near the river already had to be
taken down, the local sewage treatment plant may be next. Since 2010,
the debris flows reach as far as the hamlet Boden, threatening ten
houses and 30 inhabitants. “The next few
mudslides won’t be a big problem,” says Guttannen council leader
Hans Abplanalp. However, some houses would effectively be threatened
in two to five, others in five to seven years, he adds.

One of these homes
belongs to Martin Leuthold. “I’ve lived here for 60 years and my
father was already a farmer here,” he says. Leuthold claims he has
no fear, as he’s grown up with the moods of nature. Nevertheless,
the farmer doesn’t ignore the peril: “Perhaps nothing will happen
for the next 10 years, but maybe this summer it could all rumble down
on us. Nobody knows.”

Nearby, Hans von
Weissenfluh lives less than 20 metres away from the river. “The
threat is real, we can see it,” he says. Von Weissenfluh remembers
well how impressive amounts of water and debris came down the Aar
last summer. “Only five years ago, the river channel was much more
narrow,” he notices.

Engineers, geologists
and glaciologists assume permafrost melt to be the underlying
problem. Permafrost is underground material such as rock or rubble
that permanently remains at or below zero degrees centigrade. Ice is
a possible, but not a necessary ingredient. “The issue is, that
permafrost occurrence is generally not known,” says Nils Hählen.
There are maps designed on calculated probabilities, but as the
hydraulic engineer explains, in any case things have to be evaluated
locally.

In northeastern
mountain slopes, permafrost may occur roughly above 2,600 meters
altitude. Scientists estimate that about 5 percent of Switzerland’s
area contains permafrost. It stabilises steep rocky or scree slopes
in the high mountains and protects them from erosion by serving as a
kind of natural putty. When permafrost melts, the result may be
rockfalls and debris flows. “The lower permafrost zones are the
most vulnerable,” explains Hählen.

He locates the cause of
permafrost melt in rising air temperatures which have been measured
over the past years in the European Alps. Jeannette Nötzli,
glaciologist at the University of Zurich, mentions that atmosphere
and underground permafrost are often not directly coupled. Ice
content and changes in surface coverage can mask atmospheric signals.
Nötzli heads the Coordination Office of the Swiss Permafrost
Monitoring Network PERMOS.

“As PERMOS’
systematic monitoring commenced in 2000, most of our data cover
around a decade, whereas for robust statements about trends in
climate science typically a 30-year period is considered,” Nötzli
points out. “However,” the researcher adds, “much of our data
points to permafrost degradation. For example, in the past three
years active layer depths in summer have increased with new record
values at many of the observed sites.”

Reliable forecasting of
permafrost changes isn’t possible. In the case of Guttannen,
experts limit their predictions to the next year. Hählen expects
that in the long term, debris flows from the Ritzlihorn will stop, as
ultimately the catchment area in the flank is limited.

Removing the rubble
from the valley floor and the Aar is no option. It’s too risky, but
also too costly. Additionally, dumping places in the region are
limited. Only to remove the current rubble from the river would cost
more than 18 million Swiss Francs and accumulate to at least 50,000
lorry loads.

There’s not much hope
for the residents of Boden. Ultimately, they’ll have to leave their
homes and resettle somewhere else. Hans Abplanalp, the council
president, has talked to all persons concerned. “Nearly all of them
want to stay in Guttannen,” he says. “We can offer them land and
homes to buy.”

Boden resident Hans von
Weissenfluh plans to move up to Guttannen as soon as possible. Others
such as Martin Leuthold are more hesitant. He wouldn’t mind living
somewhere else in the village, but is reluctant to tear down his
house and move all the belongings.

“That’s a lot of
work,” he says. Leuthold fears he will not be fully compensated.
He’d only be compensated for his stable if he built a new one in
another place. “I wouldn’t know what to build a new stable for,
as I’ll soon be retired.”